The semi-solid joining process of aluminum alloy was investigated. Hyper eutectic Al-25 mass% Si alloy was melted in an electric furnace. The melt was stirred with a ceramic stirrer while cooling. The stirrer was then changed to an aluminum insert (A2017) and stirring was continued for the duration of the semi-solid temperature region. After solidification, specimens were quenched into water and sectioned for analysis of macro- and micro-structures along the weld region. The area ratio of un-bonded, melt-down and normal bonded area were measured. Effects of insertion temperature, rotation time, rotation speed, and surface conditions of specimen on bonded area ratio were reviewed. EPMA line analysis data and calculated concentration of copper were also studied, and the influence of rotation conditions on shear strength was investigated. The research shows that cast-in aluminum alloy materials can be obtained by optimizing the surface conditions of insert material, stirring temperature, and time of semi-solid processing.

抄録全体を表示

  Simulation of solidification during the local pressurization for aluminium alloy was investigated through real time modification of mesh file of casting, initial and boundary conditions with increase of pin depth. Heat transfer change and solidification processing were calculated, which provide closed loop of isothermal (solid fraction) curve indicating shrinkage porosity formation. Simulation results were in reasonable agreement with experimental results of temperature curve and observed shrinkage pore formation depending on pin squeeze condition.

抄録全体を表示

  As an attempt to optimize materials for diesel engine cylinder heads, the chemical composition and heat treatment procedure of Al-Si-Mg alloy were studied. The relation between additional elements and mechanical properties (tensile strength and elongation) was investigated on AC4C aluminum alloys containing additional Cu or Mg, and the optimum chemical composition was determined. In composition ranges within 0.6 mass%Mg or 1.0 mass%Cu, it was found that Cu or Mg addition increased tensile strength without deterioration of elongation, and also increased high cycle fatigue strength. However, thermal fatigue tests indicated that Cu addition affected thermal fatigue life. Especially thermal fatigue life markedly decreased with increasing plastic strain. In addition, excessive aging of Cu addition alloys resulted in increased thermal fatigue life. This is because the thermal fatigue life corresponding to plastic strain increases in excessively aged alloy.

抄録全体を表示

  Squeeze die casting experiments were performed to examine fluidity of AC4CH aluminum alloy in chill-vents. The results revealed that the Be-Cu mold which has large thermal conductivity decreased fluidity by 44 % compared to the SKD61 mold. From the heat transfer point of view, this kind of difference in fluidity length can be obtained only if heat resistance between the metallic mold and molten metal tip is 1/100 or less of the conventional interfacial heat resistance. This can be explained by the fact that heat resistance is extremely low at very early stage of molten metal and metallic mold contact.

抄録全体を表示

  Die casting is “a process in which molten metal is injected at high velocity and pressure into a mold (die) cavity”. Castings with smooth surfaces, high dimensional precision, complicated shapes, and reduced weight can be obtained using this process. But this process is susceptible to casting defects such as porosities, scattered chilled layers, hard spots, etc.
  For preventing casting defects, we developed “low-velocity high pressure die casting technology”, “squeeze die casting technology”, “heat insulating sleeve lubricant technology”, and “direct pouring technology”. The “direct pouring technology” is useful for producing molten metal without oxide contamination. It consists of a pumping system which supplies pure molten metal to the die casting machine. By using this technology, we have successfully reduced oxide contamination in castings to 1/20 of that of our previous castings.

抄録全体を表示